The present invention relates to a seat belt retractor which is furnished inside a vehicle, such as an automobile.
A seat belt retractor which is equipped in an automobile, and the like, has a function of retracting a part of the seat belt pulled out too much when the passenger has taken a seat, pulled out the seat belt and coupled a tongue into the buckle. In order to realize this mechanism, in the seat belt retractor of the past, a single return spring has been used. When the person fastens the seat belt and releases one""s hand after pulling out the seat belt in opposition to the force of this return spring and coupling the tongue to the buckle, the part of the seat belt pulled out too much is drawn into the seat belt retractor by the force of the return spring until it fits the body of the person.
In the seat belt retractor as explained above, it is necessary to simultaneously satisfy:
(1) that the seat belt pulled out too much is surely retracted until it fits the body of the person, and that when the person is not wearing it, the pulled out seat belt is surely housed in the housing part, and
(2) that unnecessary feeling of oppression is not provided to the chest, and the like, of the passenger when it is properly fastened.
However, with the seat belt retractor using the force of a single return spring, when a spring having weak force is used in order to lessen the feeling of oppression to the chest of the passenger when fastened, the retracting force during retraction or during housing of the belt becomes weaker, and the operability and storability are reduced. Conversely, when a spring having strong force is used in order to exhibit sufficient retracting force during retraction, there is a problem that the feeling of oppression to the chest of the passenger when properly fastened becomes greater.
Also, with the seat belt retractor of the past, because a single return spring is internally installed, there also is a problem that as the seat belt is pulled out further, the return spring is further wound and its force increases, and as the seat belt is pulled out further, the force to pull it out also increases.
As one means for solving such problems, there is an invention disclosed in Japanese Patent Publication (KOKAI) No. H3-552. This attempts to reduce the feeling of oppression of the passenger when properly fastened while assuring retracting force during retraction of the belt by using two springs as return springs, i.e. a main spring and an auxiliary spring. In detecting the coupling of the tongue and buckle of the seat belt with a detector, the forces of both the main spring and the auxiliary spring are transferred to the retraction mechanism in a state that the tongue and buckle are not coupled, and the force only of the main spring is transferred to the retraction mechanism when the tongue and buckle are coupled.
However, in this case as well, the problem that the force for pulling out the seat belt increases as it is pulled out further is not circumvented, and furthermore, a separate phenomenon has occurred such that when the seat belt is removed, as soon as the coupling of the tongue and the buckle is released, the retracting force suddenly becomes stronger, and it provides a feeling of discomfort to the passenger.
The present invention has been made in consideration of such circumstances, and it is an object of the invention to provide a seat belt retractor that surely retracts the seat belt by sufficiently great retracting force during retraction, and does not provide a feeling of oppression to the person when properly fastened, and moreover can eliminate the feeling of discomfort caused during retraction, and furthermore does not require great force when the person pulls out the seat belt.
In the first aspect for solving the aforementioned problems, a seat belt retractor includes a spring member that generates retracting force weak enough not to provide a feeling of oppression to a passenger when the passenger has fastened the seat belt, and a motor that is driven only in the direction of retracting the seat belt and generates retracting force stronger than the spring member.
In this respect, it can be made such that the retracting force is provided by the spring member when the seat belt is properly fastened, and made such that the retracting force having added retracting force by a motor to this or retracting force of the motor alone is provided to the seat belt when retracting the seat belt in a state when the tongue and the buckle are not coupled. Therefore, the seat belt can be fitted to the person with a retracting force that does not provide a feeling of oppression to the person when properly fastened, and it can be retracted with great retracting force during retraction. Also, because great retracting force is generated by the motor, even when great retracting force is suddenly applied when the coupling of the tongue and the buckle is released, there is no situation such as the tongue striking the window. As for judgment of whether it is properly fastened or retracted, it is assumed such that, in the same manner as in the past, it is considered to be a retraction time for a specified time after the coupling of the tongue and the buckle is released, and it is considered to be properly fastened in other cases including pulling out of the seat belt.
In the second aspect for solving the aforementioned problems, the motor is provided with driving force only when the tongue and buckle attached to the seat belt are not coupled.
In this second aspect, when the tongue and the buckle are coupled, it is considered that the person has finished fastening of the seat belt, and driving of the motor is not performed. Therefore, because absorption of the slack of the seat belt and fitting to the person is performed by only the force of the spring member, at this extent, a feeling of oppression is not provided to the person.
In the third aspect for solving the aforementioned problems, the motor is not provided with driving force when the seat belt is withdrawn.
In the third aspect, even if the tongue and the buckle are not coupled, when the seat belt is withdrawn in the direction of pulling out by a person, driving of the motor is stopped. Therefore, because there is no need to pull out against the driving force of the motor when the person pulls out the seat belt, it can be pulled out easily. Determination of whether or not the seat belt is driven in the direction of being pulled out can be performed, for example as shown in the example to be described later, by a switch that detects the direction of rotation of the drive shaft of the seat belt driving mechanism.
In the fourth aspect for solving the aforementioned problems, retraction by the motor is performed for only a specified time or a specified number of revolutions after coupling of the tongue and buckle is detected.
In the fourth aspect, substantially all of the slack can be absorbed rapidly by performing retraction by the motor for only a specified time or a specified number of revolutions after the seat belt is fastened, and coupling of the tongue and the buckle is detected. After that, because retraction by the spring member is performed rather than retraction by the motor, a feeling of oppression is not provided to the person.
In the fifth aspect for solving the aforementioned problems, in any of the first to fourth aspects, it is equipped with a detector that detects a direction of rotation of a spool that winds up the seat belt.
In the fifth aspect, for example when the seat belt is pulled out manually, control such as detecting that rotation and stopping the rotation of the motor can be performed.
In the sixth aspect for solving the aforementioned problems, it has a power propagation mechanism that propagates retracting force of the spring member and the motor to the seat belt, and the power propagation mechanism has a clutch mechanism that disengages the mechanical power propagation circuit between the motor and the seat belt when driven in the direction that the seat belt is pulled out by external force or when not driven in the direction that the motor retracts the seat belt.
In the sixth aspect, when the seat belt is driven in the direction of being pulled out by external force, the mechanical power propagation circuit between the motor and the seat belt is disengaged by the clutch mechanism. Therefore, because the motor does not become a load on the pulling out force, the seat belt can be pulled out with little force. Also, when the motor is not driven in the direction of retracting the seat belt, the mechanical power propagation circuit between the motor and the seat belt is disengaged by the clutch mechanism. Therefore, because the motor does not become a load on the retracting force by the spring member, the slack of the seat belt can be surely absorbed.
The seventh aspect for solving the aforementioned problems is a seat belt retractor, wherein said clutch mechanism is incorporated inside a rotating member that propagates driving force of the motor to the seat belt.
In the seventh aspect, because the clutch mechanism is incorporated inside the rotating member (for example gear or pulley) that propagates the driving force of the motor to the seat belt, the entire device can be made compact.
In the eighth aspect for solving the aforementioned problems, the clutch mechanism is directly connected to the spool that winds up the seat belt.
When the seat belt is driven in the direction of being pulled out by external force and the mechanical power propagation circuit between the motor and the seat belt wind-up unit (spool) is disengaged by the clutch mechanism, because there is considerable friction between the components, the feeling during pulling out may become poor due to the frictional resistance. If the clutch mechanism is placed within a decelerating mechanism between the motor and the spool, this friction from the side of the spool becomes greater according to the rate of deceleration, and the feeling becomes particularly poor. In the eighth aspect, because the clutch mechanism is directly connected to the spool that winds up the seat belt, the influence of the friction from the side of the spool becomes smaller, and degradation of the feeling can be controlled to a minimum.
In the ninth aspect for solving the aforementioned problems, a clutch is constituted by a roller held between an outer member and an inner member. The clutch includes a protruding part formed at the perimeter of the inner member, and it forms a wedge shape such that the interval between the perimeter of the inner member where the protruding part is not formed and the inner perimeter of the outer member is wider than the diameter of the roller in a given part and is narrower than the diameter of said roller in the part following that part. The clutch becomes an engaged state by the roller performing a wedge action by biting into the part where the interval between the perimeter of the inner member and the inner perimeter of the outer member is narrower than the diameter of the roller, and the clutch becomes a disengaged state by the roller positioned at the part where the interval between the perimeter of the inner member and the inner perimeter of the outer member is wider than the diameter of the roller.
In the ninth aspect, the roller is placed within the perimeter of the inner member and the inner perimeter of the outer member as well as the protruding part, and operation of the clutch can be performed according to whether that roller is positioned in the part where the interval between the perimeter of the inner member and the inner perimeter of the outer member is narrower than the diameter of the roller or whether it is positioned in the wider part. Therefore, it becomes possible for the clutch to operate naturally according to the direction of rotation without requiring electromagnetic power or external mechanical power, or the like, for operation of the clutch.
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In the tenth aspect for solving the aforementioned problems, the clutch comprises a second rotating member provided inside a first rotating member coaxially with the first rotating member, and a holding member provided inside the first rotating member coaxially with the first rotating member. The second rotating member has a roller holding part extending in the axial direction, and the roller is held on the roller holding part to rotate freely in contact with the inner perimeter of the first rotating member. The holding member is provided with a cut-out part for accommodating the roller, and the shape of the cut-out part is formed such that the space surrounded by the cut-out part and the inner perimeter of the first rotating member when viewed from the axial direction is narrower than the diameter of the roller at one end in the circumferential direction and is wider than the diameter of the roller at the other end. A mechanism that allows only a specified amount of relative rotation between the second rotating member and the holding member is provided on the second rotating member and the holding member.
The operation of this aspect is explained by taking an example of the case when the motor is connected to the first rotating member, and the spring member and the spool that winds up the seat belt are connected to the second rotating member in the seat belt retractor. In this respect, as will be elaborated in detail in the example described later, in the normal state, the second rotating member is urged by the force of the spring member to rotate, for example, counterclockwise.
By this, the roller together with the roller holding part is also forced to revolve counterclockwise, and the extended part of the holding member is pushed counterclockwise. Accordingly, the holding member also rotates counterclockwise, the second rotating member and the holding member both rotate inside the first rotating member, and their rotational forces are not relayed to the first rotating member. Therefore, for example, the mechanical power propagation circuit between the motor, and the spring member and the seat belt becomes in a disengaged state, and the motor does not become a load on the spring member.
When the first rotating member is driven counterclockwise by the motor driven in the direction of retracting the seat belt, the roller is placed between the inner perimeter of the first rotating member and the cut-out part of the holding member (on the end having a space narrower than the diameter of the roller). Therefore, the roller receives counterclockwise revolving force by the friction between the roller and the inner perimeter of the first rotating member, and the second rotating member also receives counterclockwise force by way of the roller holding part.
Because the roller comes in contact with the end of the cut-out part of the holding member and pushes the holding member, the holding member rotates counterclockwise and attempts to escape, but because a limit is provided to the amount of relative rotation between the holding member and the second rotating member, the amount of escape of the holding member is limited, and in the end, when the amount of relative rotation between the holding member and the second rotating member has reached the limit, the roller is placed between the inner perimeter of the first rotating member and the cut-out part of the holding member and rotates together with the first rotating member, and its driving force comes to be propagated to the second rotating member. In this state, for example, the power propagation circuit between the motor shaft, and the spring member and the seat belt comes to engage mechanically.
For example, when the seat belt is driven in the direction of being pulled out by a person pulling out the seat belt, and the second rotating member is driven clockwise, the roller also revolves counterclockwise by way of the roller holding part, it hits the end of the cut-out part of the holding member (opposite to the end previously described), and pushes the holding member clockwise. At this time, the roller is positioned at the end within the space formed by the inner perimeter of the first rotating member and the cut-out part of the holding member where it is formed wider than the diameter of the roller. Therefore, the rotational force of the second rotating member is not relayed to the first rotating member. Therefore, for example, the mechanical power propagation circuit between the roller, and the spring member and the seat belt becomes in a disengaged state. Therefore, for example, when the seat belt is pulled out, the motor does not become a load on the pulling out force, and the pulling out of the seat belt can be performed easily.
In the eleventh aspect for solving the aforementioned problems, the clutch comprises a rotating member (second rotating member) provided inside a first rotating member coaxially with the first rotating member and being mechanically connected to a spool that winds up the seat belt and the spring member, a holding member provided inside the first rotating member coaxially with the first rotating member, and a roller. The second rotating member has a bump on one side, and the holding member has a perimeter part where the distance from the center changes continuously, a protruding part formed by extending outward a part of the perimeter part, and a spring member. When the second rotating member, the holding member, and the roller are incorporated in the first rotating member, the roller is positioned so as to be held within the inner perimeter of the first rotating member, the perimeter part of the holding member, the protruding part of the holding member, and the bump of the second rotating member. The interval between the inner perimeter of the first holding member and the perimeter part of the holding member is made larger than the diameter of the roller at the wide part and is made wider than the diameter of the roller at the narrow part. The spring member is disposed so as to urge the roller in the direction where the interval between the inner perimeter of the first rotating member and the perimeter part of the holding member becomes narrow.
The operation of this aspect is explained by taking an example of the case that the motor is connected to the first rotating member, and the spring member and the spool that winds up the seat belt are connected to the second rotating member in the seat belt retractor. In this aspect, as will be elaborated in detail in the section later, assuming that, for example, in the normal state, the second rotating member is urged by the force of the spring member to rotate, for example, counterclockwise, and the interval between the inner perimeter of the first rotating member and the perimeter part of the holding member is made wider toward the clockwise direction.
When the second rotating member is rotated counterclockwise, its bump collides with the protruding part of the holding member, and it causes the holding member to rotate counterclockwise. Then, the roller is repelled by the force of the spring and moves clockwise relative to the holding member, and it comes to a position where the interval between the inner perimeter of the first rotating member and the perimeter part of the holding member is larger than the diameter of the roller. Therefore, the mechanical coupling between the holding member and the first rotating member is separated, and the rotational force of the holding member is no longer relayed to the first rotating member. That is, because the rotational force of the second rotating member is not relayed to the first rotating member, for example, the mechanical power propagation circuit between the motor, and the spring member and the seat belt becomes in a disengaged state, and the motor does not become a load on the spring member.
For example, when the motor is driven in the direction of retracting the seat belt and the first rotating member is driven counterclockwise, the roller comes to be pushed counterclockwise by the force of the spring up to the part where the interval between the inner perimeter of the first rotating member and the perimeter part of the holding member becomes equal to the diameter of the roller. Thus, it is pushed in the direction where the interval between the inner perimeter of the first rotating member and the perimeter part of the holding member becomes narrower than the roller, the roller becomes a wedge and is tightly held between the inner perimeter of the first rotating member and the perimeter part of the holding member, and the rotational force of the first rotating member is propagated to the holding member, so that the holding member and the roller rotate together with the first rotating member.
When the roller goes on to rotate, i.e. revolve, together with the first rotating member and the holding member, it collides with the bump of the second rotating member, and pushes the bump in the counterclockwise direction. Therefore, by this force, the second rotating member comes to rotate in the counterclockwise direction together with the first rotating member. That is, in this case, the first rotating member and the second rotating member are coupled through the clutch, and for example, the rotational force of the motor comes to be propagated to the spring member and the spool of the seat belt.
For example, when the seat belt is driven in the direction of being pulled out by a person pulling out the seat belt and the second rotating member is driven in the clockwise direction, the bump of the second rotating member collides with the roller, overcomes the force of the spring, and causes the roller to move in the clockwise direction. By this, the roller collides with the protruding part of the holding member and causes the holding member to rotate in the clockwise direction.
As described before, because the interval between the inner perimeter of the first rotating member and the perimeter part of the holding member becomes wider toward the clockwise side, when the roller moves in the counterclockwise direction, it comes to a position where the interval between the inner perimeter of the first rotating member and the perimeter part of the holding member is greater than the diameter of the roller. Therefore, the mechanical coupling between the holding member and the first rotating member is separated, and the rotational force of the holding member is no longer relayed to the first rotating member. That is, because the rotational force of the second rotating member is not relayed to the first rotating member, for example, the mechanical power propagation circuit between the motor, and the spring member and the seat belt becomes in a disengaged state, and the motor does not become a load on the pulling out force of the seat belt, so that the pulling out can be performed easily.
In the twelfth aspect for solving the aforementioned problems, a seat belt retractor includes the device disclosed in any of the ninth to eleventh aspects.
In this aspect, the rotational force of the motor can be propagated to the retraction apparatus without using special control or power, and the motor can be made such that it does not become a load on the spring member when pulling out the seat belt. It goes without saying that when the tenth aspect and the eleventh aspect is used, the first rotating member is connected to the motor side, and the second rotating member is connected to the spool that winds up the seat belt.